This invention relates in general to the field of railway tank cars and, in particular, to a railway tank car having a lading heating system.
Railway tank cars may be used to move hazardous and non-hazardous liquid or semi-liquid bulk freight of all types including, but not limited to: liquified petroleum gases; liquified gases (e.g., carbon dioxide); chemical intermediates; polymers; antiknock compounds; anhydrous ammonia; chlorine, alcohol, vegetable and fish oils; fruit juices; wine and syrups. Modern tank cars are typically designed without center sills and rely on the structural strength of the tank to transmit draft and buffing forces. Many of the tank cars currently in use can carry in excess of one hundred tons and often have a thirty-thousand gallon capacity. Tank cars which are either heated, pressurized, lined, or a combination of these features, are available to shippers.
Heated tank cars may be used to carry liquids which are highly viscous at low temperatures. Heating panels, internal pipes, or heating coils, may be applied within or external to the tank car in order to increase the temperature of the lading, during unloading operations. These panels, coils or pipes may be fed by a heating fluid such as steam, hot water or hot oil.
Heating panels, and their associated piping and coils which carry the heating fluid, decrease the capacity of the railway car by decreasing the available volume within the tank. The specific configuration of heating panels and associated coils may also affect the performance of the tank car during unloading. For example, many tank cars distribute heat disproportionately to the contents of the car. Accordingly, a portion of the contents may become overheated, which may be detrimental to certain liquids which may solidify or caramelize. Underheated contents will not unload efficiently. A combination of these factors may lead to a phenomenon referred to as xe2x80x9cheelxe2x80x9d wherein solidified contents remain within the car after unloading and decrease the overall capacity of the car. Heel is also detrimental to heat transfer of the piping and coil system and may contaminate subsequent lading within the tank car.
Traditional interior piping and exterior coil configurations do not efficiently distribute the heating fluid throughout the system. Furthermore, improper drainage of the heating fluid and/or condensate by-product can lead to failure of the heating system.
In accordance with teachings of the present invention, disadvantages and problems associated with previous heated railway tank cars have been substantially reduced or eliminated.
In one embodiment of the present invention, a railway tank car including a tank coupled with first and second stub sill assemblies may be provided. The stub sill assemblies may each be coupled with associated railway car truck assemblies. A tank defined in part by a generally elongate hollow cylinder having first and second ends with first and second heads mounted respectively thereon, may also be provided. In a particular embodiment, one or more heat transfer panels may be disposed within the cylinder adjacent the first and second heads. Each of the heat transfer panels may communicate with respective pluralities of heat transfer ducts, operable to provide a heating medium to the first and second heat transfer panels.
In another embodiment, a first support member may be disposed within the cylinder, intermediate a discharge valve of the tank, and head. A second support member may also be disposed within the cylinder, intermediate the discharge valve and an opposing head. Each support member may provide support for, and maintain their respective heat transfer panels in a spaced relation with a lower portion of the cylinder.
In still another embodiment, each support member may comprise an arcuate shaped bar disposed axially along the lower portion of the cylinder along a plane approximately perpendicular to a longitudinal centerline of the cylinder. Alternatively, each support member may comprise a generally arcuate shaped angle disposed in a similar manner as described above with respect to the bar.
In yet another embodiment, each heat transfer duct may be disposed upon an exterior portion of the cylinder, being in fluid communication with the heat transfer panels.
A technical advantage of the present invention includes a lading heating system which minimizes any reduction in available volume for carrying lading in the tank car. The reduced size of the heat transfer panels and the exterior location of the heat transfer ducts provides for maximum capacity of the interior of the tank. Also, placing the heat transfer ducts on the exterior of the tank maximizes heat transfer at the bottom of the tank and increases the efficiency of the heating system. This allows for a reduction in overall weight of the heating system, thereby increasing payload capacity.
Another technical advantage of the present invention includes the increased strength of the railway tank car provided by the installation of the support members, heat transfer ducts, coils and heat transfer panels. The location of the support members on the tank shell, near the heads, provides support to the tank where the highest train loads are supplied to the tank, at the end of the draft sill. Also, the ducts, coils and heat transfer panels provide support and increase the moment of inertia of the tank.
Still another technical advantage of the present invention includes the increased duct width and reduced duct height which spread the heating media into a thin film over a larger area, thereby increasing the heat transfer efficiency. The increased duct width also reduces the number of ducts required to efficiently cover the desired heating surface.
Yet another technical advantage of the present invention includes the reduction and/or elimination of heel. Accordingly, heat transfer is accomplished more efficiently without the loss of volume typically accompanied by heel, and lading contamination is substantially reduced.
Other technical advantages are readily apparent to one of ordinary skill in the art from the following figures, descriptions, and claims.